dBm to Watts Calculator: Convert RF Power Instantly

dBm to Watts Calculator

Convert RF power between dBm and Watts (bidirectional)

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dBm is used in RF and telecom to express power on a logarithmic scale relative to 1 milliwatt (mW). It compresses a huge power range into small, easy-to-compare numbers.

0 dBm = 1 mW. Every +3 dBm roughly doubles the power, and every +10 dBm multiplies power by 10×. So 30 dBm = 1000 mW = 1 W, and 10 dBm = 10 mW = 0.01 W.

Formula: watts = 10^{(dBm − 30) / 10}, and reversed: dBm = 10 × log₁₀(watts × 1000).

dBm

Watts

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Quick Reference

RF and telecom power specs use dBm, a logarithmic scale that compresses an enormous power range into manageable numbers, this calculator converts dBm to watts and back.

How to use this dBm to Watts calculator

Enter a value in the dBm field to see the equivalent in Watts.
Or enter a value in the Watts field to see the equivalent in dBm, either field updates the other automatically.

What this calculator does

dBm is used in RF and telecom to express power on a logarithmic scale relative to 1 milliwatt (mW). It compresses a huge power range into small, easy-to-compare numbers. 0 dBm equals 1 mW. Every +3 dBm roughly doubles the power, and every +10 dBm multiplies power by 10 times. So 30 dBm equals 1000 mW (1 W), and 10 dBm equals 10 mW (0.01 W).

Watts = 10^((dBm − 30) ÷ 10)
dBm = 10 × log₁₀(Watts × 1000)

Why RF engineering uses a logarithmic scale

RF power levels can span from picowatts (extremely weak signals) to kilowatts (transmitter output), a range of many orders of magnitude that would be unwieldy to compare directly in watts. The logarithmic dBm scale compresses this entire range into small, easy-to-compare numbers, and critically, makes gain and loss calculations (which multiply in linear watts) become simple addition and subtraction in dBm, which is why the entire RF and telecom industry standardizes on it.

Frequently asked questions

What does 0 dBm equal in watts?

0 dBm equals exactly 1 milliwatt (0.001 watts), the reference point the dBm scale is built around.

Why does RF engineering use dBm instead of watts directly?

RF power spans an enormous range (picowatts to kilowatts), and the logarithmic dBm scale compresses that range into manageable numbers while turning gain/loss multiplication into simple addition and subtraction, which is much easier to work with in practice.